Novel stabilizers for organic materials subject to degradation, 2,4,6-tris(substituted phenoxy)-1,3,5,2,4,6-trioxatriphosphorinanes that form effective stabilizer combinations with hindered phenol compounds, particularly hydroxyphenylalkyleneyl isocyanurates, have been prepared by the reaction of substituted phenylphosphorodichloridites, water and triethylamine in tetrahydrofuran. At least one other solvent is required to isolate and purify the product for use. A less complex single solvent process that also provides improved yields of product of a higher purity is desired.